Contact plates, also known as culture dishes or Petri dishes, are widely known and used in laboratories for growing cell cultures, bacteria cultures, and the like. Conventional contact plates are comprised of two parts: (1) a base, which is typically a shallow open-ended cylindrical container; and (2) a cover, which is wider in diameter than the base, and fits over and covers the base.
Conventional contact plates are difficult for the user to lift and move because the cover is wider in diameter than the base and is loosely positioned over the base. In particular, the user must ensure that he or she has a firm grasp on both the base and the cover when lifting and moving the contact plate. Accordingly, either both hands are required to grasp and lift the contact plate, or the user must slide the entire contact plate off the edge of the working surface to grasp the contact plate. Alternatively, in order to lift and support the base, the user must tilt the contact plate to facilitate the positioning of his or her fingers underneath the base. This is undesirable because the tilting can shift and disturb the contents of the contact plate. Tilting of the contact plate may also cause the cover to slide; thus, making it awkward for the user to get a firm grasp on the contact plate.
Conventional contact plates are prone to accidental or inadvertent opening which may contaminate the culture. Conventional contact plates are often stacked together on the working surface, in the incubator, or in the storage area for space efficiency. As the cover of a conventional contact plate is loosely positioned over the base, the cover can be accidentally opened when the stacked contact plates are handled. In addition, the cover of a contact plate may open if the contact plate is jostled during handling. Thus, it is highly desirable to have contact plates which prevent accidental openings.
Various contact plates have been provided in which the cover is placed over the base in a snug or tight fit. However, this leads to inefficiency as the user must use both hands to open and remove the cover.
Various contact plates have been provided in the prior art, which attempt to create handles on the contact plate to facilitate the lifting of the contact plate from the work surface. U.S. Pat. No. 3,649,463 discloses a Petri dish with a handle portion extending around the outer surface of the base. U.S. Pat. No. 5,856,176 discloses a culture dish with a pair of handles extending from the base, the cover, or both. However, contact plates with external handles take up more space on the work surface, in the incubator, and in the storage area. Since a large number of contact plates are typically used at one time, this decreases the efficiency of the laboratory as fewer culture dishes can be used at a time.
Contact plates have been provided in the prior art, which attempt to create a mechanism for securely positioning the cover over the base. U.S. Pat. No. 5,725,123 discloses a cover with individual elevations on the inner surface of the cover apron, which press against the outer surface of the base wall to secure the cover to the container. However, this is not a reliable method for securing the cover to the base because the cover is only frictionally held to the base. Over time, the shape of the cover or container may change and affect the ability of the individual elevations to contact the base wall.